A white screen, a slow page, a plugin conflict with no obvious cause, guessing your way through these wastes time. Debugging tools replace guesswork with actual data: which query is slow, which function is deprecated, which plugin is throwing the error. Here are 10 real, current options, with one dead one flagged.
Why These Tools Matter
Without real debugging data, a small problem tends to become a bigger one, someone tries a random fix, it doesn’t work, and now there are two problems instead of one. These tools show you the actual line, query, or plugin causing an issue instead of making you guess.
The cost of skipping proper debugging tools isn’t just wasted time either. A trial-and-error approach to fixing a WordPress site often means deactivating plugins at random, editing files without a backup, or applying a fix pulled from a forum post that addressed a completely different underlying issue. Each of those carries its own risk of making things worse. Real debugging data turns a fix from a guess into a targeted change.
This list sticks to tools that are currently maintained, clearly labeled where they’re not, and genuinely useful rather than padding out a round number. A couple of once-popular options got dropped or flagged specifically because recommending outdated or abandoned software does more harm than leaving it off entirely.
10 WordPress Debugging Tools
1. Query Monitor
Query Monitor is the standard tool for this: a full breakdown of database queries and how long each takes, right in an admin bar dropdown, no server access needed. Also surfaces PHP errors, HTTP requests, hooks, and enqueued scripts. The closest thing to a must-have on this list for anyone doing real theme/plugin work.
What makes it genuinely essential rather than just convenient is the panel breaking down exactly which template files loaded, in what order, and how long each hook took to fire. When a page feels sluggish and nobody can say why, Query Monitor usually points straight at the offending plugin’s query or a template file doing something it shouldn’t, within a minute or two of activating it.
2. Debug Bar
Adds an admin bar menu with query counts, load times, and background errors. Worth a caveat: it’s community-maintained (20,000+ installs) and recent user reviews report PHP errors under newer WordPress versions, functional but worth testing on staging before relying on it heavily.
3. WP Debugging
Turns on WordPress’s built-in debug constants (WP_DEBUG, SCRIPT_DEBUG, and others) without hand-editing wp-config.php. The safest starting point if you’ve never touched debug settings directly and don’t want to risk a typo in a config file.
This matters more than it sounds like it should. A single misplaced character in wp-config.php can take an entire site down with a fatal error, and that file often doesn’t have version history the way a theme file might. Letting a plugin toggle these constants for you removes that specific risk entirely, which is worth the small tradeoff of running one more plugin.
4. New Relic (with WordPress integration)
Server-level performance monitoring, not WordPress-specific, but genuinely useful paired with a WordPress plugin for tracking per-plugin/theme load time and server resource use. Requires a New Relic account; worth it for high-traffic sites or client work where WordPress-only tools don’t show the full picture.
The distinction worth understanding here is that Query Monitor and most of the other tools on this list only see what’s happening inside a single WordPress request. New Relic sees the server itself, memory usage, CPU load, database connection pooling, which matters when a slowdown isn’t actually WordPress’s fault but a server resource ceiling being hit under real traffic.
5. Health Check & Troubleshooting
An overall site health report (PHP version, plugin conflicts, server settings) plus a genuinely useful Troubleshooting Mode: disables all plugins and switches to a default theme for you only, visitors see the site unaffected while you test. One of the safer tools on this list precisely because of that isolation.
That isolation is the real selling point. The classic debugging advice of “deactivate all your plugins and see if the problem goes away” is genuinely useful, but doing it on a live site means every visitor loses functionality while you troubleshoot. Health Check’s session-based troubleshooting mode gets you the same diagnostic clarity without that tradeoff.
6. Error Log Monitor
Free (WordPress.org, 20,000+ installs, updated within the last year, tested to WordPress 6.8). Surfaces your server error log directly in the WordPress dashboard instead of requiring hosting-panel access, with a quick-glance widget for recent errors.
7. Simple History
Logs plugin installs, logins, post edits, and settings changes. Doesn’t fix anything itself, but when something breaks after a change nobody remembers making, this is often the fastest way to find out what actually changed and when.
On sites with more than one person able to log in, this tool earns its place fast. “It was working yesterday” is a common starting point for a support ticket, and Simple History turns that vague statement into an actual timeline: who logged in, what plugin got updated, which setting got flipped, all timestamped and searchable instead of relying on someone’s memory of what they clicked.
8. Debug Log Manager
Debug Log Manager (free, WordPress.org, 10,000+ installs, updated within the last month) gives you a readable dashboard view of your debug.log file, with filtering and clearing built in, instead of downloading and scrolling through a raw text file via FTP.
9. Debug This
Debug This adds an admin bar link for instant per-page info: which template is loading, current queries, user info. Lightweight, useful for quickly confirming which template file is actually rendering a given page.
This one earns its spot specifically for theme development work. When a page isn’t pulling the template file you expect it to, and WordPress’s template hierarchy rules aren’t obvious from the file structure alone, Debug This answers the question in one click instead of adding temporary debug output to half a dozen candidate template files.
Dropped From This List: Developer (by Automattic)
An earlier version of this post recommended “Developer” by Automattic. It was permanently closed on WordPress.org in October 2025 at the author’s own request and can no longer be installed. Query Monitor and the Health Check tool above cover the same general “set up my debugging environment properly” ground.
One More Worth Flagging: Log Deprecated Notices
This plugin (helpful for finding outdated function calls before they break) carries WordPress.org’s own “not tested with the latest 3 major releases” warning, last updated roughly 5 years ago, tested only to WordPress 5.8. Not necessarily broken, but a real risk on a current WordPress install, test on staging first if you still want to use it.
Building a Debugging Workflow, Not Just a Toolbox
Installing every tool on this list at once doesn’t actually make debugging faster, it usually just adds admin bar clutter and a few more plugins to keep updated. A more useful approach is matching the tool to the symptom. A slow-loading page points you toward Query Monitor first, since it’ll show the specific query or hook eating the time. A white screen with no visible error points you toward WP Debugging to safely turn on error output, then the server’s error log via Error Log Monitor or Debug Log Manager to see what actually broke.
A “something changed and nobody knows what” situation points straight at Simple History, and a “is this my theme, my plugins, or my host” question points at Health Check’s isolated troubleshooting mode. Treat these as a targeted toolkit rather than a permanent installed set, and you’ll spend less time managing debugging plugins and more time actually fixing things.
Reading a Debug Log Without Getting Overwhelmed
A raw debug.log file on an active site can run to thousands of lines fast, most of them harmless notices that have nothing to do with the actual problem. Filter for the word “Fatal” first, since a fatal error is the one guaranteed to be causing a visible problem right now. From there, PHP warnings and deprecated notices are worth reviewing but rarely explain a white screen on their own, they’re more useful for catching problems before they become fatal on a future WordPress or PHP update.
Timestamps matter more than people initially treat them. If a client reports a problem starting “sometime this morning,” cross-reference that window against the log rather than reading the entire file top to bottom. Combined with Simple History’s change log, narrowing to a specific time window usually surfaces the actual cause within a few minutes instead of an hour of scrolling.
Server-Side Tools vs. Browser DevTools
Everything covered so far runs inside WordPress and looks at what’s happening on the server: which query ran, which plugin fired, which function is deprecated. That’s a different layer entirely from the browser’s own developer tools, which show what’s happening after WordPress has already generated the page, JavaScript errors, failed network requests, render-blocking assets, layout shifts.
Both matter, and confusing which layer a problem lives in wastes time. A broken contact form that submits but does nothing is often a JavaScript console error, invisible to Query Monitor no matter how carefully you read its output. A page that loads correctly but takes eight seconds to appear is much more likely a server-side query problem that browser DevTools won’t explain, since from the browser’s perspective it’s just waiting on a slow response. When a problem doesn’t make sense from the WordPress side, check the browser console before assuming the debugging plugin is missing something.
When to Escalate Beyond These Tools
These tools are genuinely good at diagnosis, but diagnosis isn’t the same as a fix. Query Monitor can tell you a specific plugin is running an unindexed query that takes two seconds, but fixing that means either the plugin author patching it, a custom index added at the database level, or replacing the plugin entirely, none of which the diagnostic tool itself does for you.
Know your own limits going in. If a debugging tool points at a specific line of a plugin’s code and the fix means editing that code directly, that’s usually a signal to bring in a developer rather than attempting a patch you can’t fully evaluate the consequences of. Diagnosis narrows the problem down to something specific and describable, which is valuable even if you’re not the one implementing the fix, since it turns a vague support request into a precise one a developer can act on immediately.
Bringing a developer a Query Monitor screenshot showing the exact slow query, or a Simple History log showing exactly when a plugin update coincided with the problem starting, cuts their diagnosis time down dramatically compared to a vague “the site feels slow” or “something broke.” That upfront work on your end often means the difference between a quick, cheap fix and a longer, more expensive investigation.
Choosing One
Query Monitor first, it covers the most ground and is actively maintained. WP Debugging or Health Check if you’re not comfortable editing config files directly. Error Log Monitor or Debug Log Manager if server error logs are specifically what you need visibility into. Simple History if you need to know who changed what, not just what broke.
Setup and Safety Notes
- Install from Plugins > Add New like any plugin; a few (WP Debugging especially) toggle settings in
wp-config.phpfor you rather than requiring manual edits. - Turn debugging off on live sites once you’re done. Exposed error messages and debug output are both a security risk and a performance drag for real visitors.
- Test any debugging plugin on a staging copy first if the site is business-critical. Even a lightweight monitoring plugin adds some overhead, and a poorly maintained one carries its own risk of conflicts.
- Remove or deactivate debugging plugins you’re not actively using rather than leaving them installed indefinitely. Every active plugin is one more thing that needs updates and one more potential point of conflict down the line.
Common Mistakes That Make Debugging Take Longer
The most common mistake is changing more than one thing at a time. Deactivating three plugins simultaneously and finding the error is gone tells you one of the three was the problem, not which one, and you’re back to a second round of trial and error to isolate it. Change one variable, test, then move to the next. It feels slower in the moment but it’s almost always faster overall than the alternative of retracing steps after a multi-variable change.
A second mistake is debugging directly on a live production site without any isolation, whether that’s Health Check’s troubleshooting mode, a staging environment, or at minimum a maintenance mode message for visitors. Deactivating plugins or switching themes on a live site to test a theory means every visitor experiences whatever broken or incomplete state you’re testing, which is a real cost even if the fix only takes ten minutes to find.
A third mistake is trusting the first error message you see as the actual root cause. WordPress and PHP often surface a symptom rather than the original trigger, a fatal error on line 400 of a file might be a direct consequence of bad data passed in from a completely different plugin earlier in the request. Query Monitor’s hook and query timeline is particularly useful here because it shows the sequence of what happened, not just the final failure point.
Frequently Asked Questions
Do I need to hire a developer to use these tools?
No. Query Monitor, Health Check, and WP Debugging are all built for exactly this, giving a non-developer enough information to describe a problem accurately, even if the actual fix still needs a developer’s help.
Will debugging plugins slow down my live site?
Most add negligible overhead when installed but not actively displaying data, though a few, particularly ones logging every query in detail, can add noticeable load on high-traffic sites. That’s part of why turning debugging off once you’re done matters, not just for security.
Can I run more than one of these tools at once?
Yes, though Query Monitor and Debug Bar overlap enough in function that running both rarely adds value. Combining Query Monitor with Simple History or Health Check covers more distinct ground than stacking multiple query-focused tools.
What’s the very first thing to check when a site goes down?
Enable WP_DEBUG through WP Debugging or check the server’s raw error log through Error Log Monitor before touching anything else. A fatal error message almost always names the specific file and line causing the crash, which turns a guessing game into a two-minute fix.
How do I know if a debugging plugin itself is abandoned or unsafe to install?
Check the plugin’s WordPress.org page for the last update date and which WordPress version it’s tested against. A plugin untouched for several years and untested against recent releases, like the Log Deprecated Notices example above, isn’t automatically broken, but it’s worth trialing on staging before trusting it on a live site.